“Without prejudice to regulation 43H below, for the purposes of section 80(3) of the Act (defence by the Commissioners that crediting by them of an amount claimed would unjustly enrich the claimant) reimbursement arrangements made by a claimant shall be disregarded except where they—

(a) include the provisions described in regulation 43C below; and(b) are supported by the undertakings described in regulation 43G below.”